Anti-shock reversing-drive screw actuator unit

ABSTRACT

A rotatively restrained nut is fixedly connected through the agency of sleeve, plug and other components to a member which is to be reversibly driven axially, for example, a periodically reversed reciprocable ram or plunger, the nut and connected assembly being operated for the purpose by an elongated, axially fixed motor-driven screw. At an end of its stroke in one direction the nut bottoms against an impact washer and, through the latter, against a resilient cushioning stop pad. The stop surrounds the corresponding end of the rotary screw and is restrained from axial movement relative to the screw by a cupped retainer member, which also limits the extent of radial expansion of the pad under axial compression by the nut. As thus additionally loaded in torsion, at the instant of a resiliently cushioned engagement of the nut in thus bottoming and coming to an axial stop, the screw imposes an instantaneously increased load on the drive motor with the result that, through the agency of a sensitive device, a centrifugal reversing switch, a built-in limit switch means, or like conventional agency, the direction of rotation of the motor and screw is reversed. The nut assembly operated thereby commences travel in the opposite direction, aided in a cushioned start by resilient wind-up energy stored in the cushion at the time of engagement by the nut. Reaching the end of this reversed stroke, further axial travel of the nut is mechanically halted; and there results again an increase of torque load on the motor, due in this case to reactive tensile force exerted by the screw on the cushion to compress the latter in coming to a halt. The motor again is reversed, as assisted in a soft start by a torque wind-up effect at the cushion.

United States Patent [191 Ritchie [11] 3,743,909 [4 1 July 3,1973

[ ANTI-SHOCK REVERSlNG-DRIVE SCREW ACTUATOR UNIT Lyle J. Ritchie, St. Clair Shores,

Mich.

[73] Assignee: Automatic Refuse Systems, Inc., St.

Clair Shores, Mich.

[22] Filed: Mar. 8, 1972 [21] Appl. No.: 232,786

[75] Inventor:

Primary Examirier--Bernard A. Gilheany Assistant Examiner-Thomas Langer Att0rney-Franklin E. Quale [5 7] ABSTRACT A rotatively restrained nut is fixedly connected through the agency of sleeve, plug and other components to a member which is to be reversibly driven axially, for example, a periodically reversed reciprocable ram or plunger, the nut and connected assembly being operated for the purpose by an elongated, axially fixed motor-driven screw. At an end of its stroke in one direction the nut bottoms against an impact washer and, through the latter, against a resilient cushioning stop pad. The stop surrounds the corresponding end of the rotary screw and is restrained from axial movement relative to the screw by a cupped retainer member, which also limits the extent of radial expansion of the pad under axial compression by the nut. As thus additionally loaded in torsion, at the instant of a resiliently cushioned engagement of the nut in thus bottoming and coming to an axial stop, the screw imposes an instantaneously increased load on the drive motor with the result that, through the agency of a sensitive device, a centrifugal reversing switch, a built-in limit switch means, or like conventional agency, the direction of rotation of the motor and screw is reversed. The nut assembly operated thereby commences travel in the opposite direction, aided in a cushioned start by resilient wind-up energy stored in the cushion at the time of engagement by the nut. Reaching the end of this reversed stroke, further axial travel of the nut is mechanically halted; and there results again an increase of torque load on the motor, due in this case to reactive tensile force exerted by the screw on the cushion to compress the latter in coming to a halt. The motor again is reversed, as assisted in a soft start by a torque wind-up effect at the cushion.

16 Claims, '3 Drawing Figures United States Patent [1 v [111- 3,743,909

Ritchie [451 July 3, 1973 ANTI-SHOCK REVERSING-DRIVE SCREW ACTUATOR UNIT BACKGROUND OF THE INVENTION 1. Field of the Invention The reversing drive screw actuator of the invention will find application in many fields in which it is desired to effect an instantaneous cushioned reversing of a reciprocatory stroke in either axial direction, without substantial shock and consequent noise and undue strain on parts. The unit is currently being installed in trash compactors of the type illustrated and described in the patent to Gray and Ritchie, U.S. Pat. No. 3,589,277, of June 29, 1971, in which periodic reversals of direction of axial movement of a compacting ram are involved. However, other and more general types of installation are contemplated.

2. Descriptionof the Prior Art A search reveals the following patents, to Robertson U.S. Pat. No. 1,644,545 of Oct. 4, 1927 Lockett U.S. Pat. No. 2,060,997 of Nov. 17, 1936 King et al. U.S. Pat. No. 2,322,637 of June 22, 1943 Miles U.S. Pat. No. 2,439,094 of Apr. 6, 1948 Morton U.S. Pat. No. 3,296,513 of Jan. 3, 1967. Of these, Robertson, Lockett, and Miles relate to power operated reversing devices and circuitry essentially relying upon external limit switch means for timing of reversals of stroke direction. King et al. and Morton relate to special load sensing voltage control circuitry, whereas entirely conventional and widely available electrical circuit arrangements and means are contemplated for controlling the subject actuator unit.

SUMMARY OF THE INVENTION cally present at only one end of the stroke, as, for example, when a ram as mechanically driven through the agency of a rotatively fixed, axially traveling nut mating with a drive screw, reaches one extreme end of a trash compressing stroke, the soft" cushioned reversing axial action is, nevertheless, the same at both ends of axial travel of the nut and ram. Thus, loud metallic clicks signalling stroke reversal are not present. There are no sudden build-ups of electrical loads the loads as imposed on the motor are very low, indeed; and it follows that lesser mechanical stresses are imposed on all associated drive components, such as keys, pulleys, gears and the like.

More in detail in the structural sense, the operating nut of the unit is, in effect, connected to reciprocatively drive a ram, plunger or the like operated element through the agency of an elongated tubular inner sleeve component which is guided in an outer sleeve and is fixedly connected at one axial end thereof to the operated element, such as the compactor ram instanced above. As illustratively depicted herein, it is this ram,

inner sleeve, which prevents rotation of the drive nut, since the sleeve has a welded connection to the ram at one end thereof and a radially pinned upper plug connection to the nut at its opposite end. However, many alternative ways are available for preventing rotation of the axially traveling operator element, in this case the nut of the nut and screw unit.

It is adjacent a lower welded plug connection of the inner sleeve that the compressible cushion of the reversing subassembly is located. This is in the form of a cylindrical pad of urethane or other compressibly deformable like material, against which 'pad an impact washer is superposed to receive the thrust of the operator nut at the lower end of the latters stroke; the result of this is a cushioned wind-up of torque to assist a starting of the reversed stroke outset, consequent to momentarily increased motor torque transmitted through the operator screw. As engaged in axial compression the cushioning pad expands radially, but control of its size, shape and, accordingly, a finite limitation of its elastic limit, is effected through a cupped retainer stop in which the cushion pad is received, the cup wall rigidly confining radial expansion of the pad.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an upright elevational view of the unit of the invention as connected typically at a lower end to a compressor plunger or ram and driven at its upper end by an electric motor, the view being partially broken away and sectioned in a vertical plane including the axis of nut and screw operator components;

FIG. 2 is a view in horizontal section on broken line 2-2 of FIG. 1, showing'arrangements for coupling an inner ram-connected sleeve of the unit to the operator nut through plug and radial set screw means; and

FIG. 3 is a fragmentary view in horizontal section on line 3-3 of FIG. 1, showing a nut rotation-preventing detail.

DESCRIPTION OF A PREFERRED EMBODIMENT As illustrated in FIG. 1, the anti-shock reversing actuator unit of the .invention, generally designated by the reference numeral 10, is fixedly sustained in a vertical setting by an appropriately braced bracket structure 1 1 mounting a rugged cylindrical collar 12. This, in turn, through top and bottom welded connections, rigidly supports in an upright position an axially elongated, fixed outer cylindrical sleeve 13 of the unit. However, obviously, different orientations of the unit as a whole are contemplated and, equally obviously, its outer sleeve 13 may be sustained by many other types of support.

As herein shown, sleeve 13 telescopingly receives and guides, with a fairly close tolerance sliding fit, an inner elongated sleeve 14 of the unit 10, which at its lower axial end telescopes onto a cylindrical bottom plug 15, being rigidly and unitarily connected to the latter at an annular weld 16. Plug 15, in turn, is fixedly connected by a large head screw 17 at the axis of sleeve 14 to the operated member 18 of the unit 10, which has been instanced above as being a ram or plunger plate of a trash or rubbish compressor of the sort disclosed in the Gray and Ritchie patent. An auxiliary pin 19 locks the bottom plug 15 of sleeve 14 against rotation I about the axis of attaching screw 17.

as itself confined against rotation about the axis of the As appears in FIG. 3, the ram member 18 is rectangular in outline, being guided in a correspondingly crosssectioned bag holder H of the compactor (not part of the invention); and it is through this nested arrangement that rotation of plug and inner sleeve is restrained, the motion of the latter being solely axial. Rotation of the operating nut of unit 10 is correspondingly prevented through agencies hereinafter described. It is in order to note again that many other types of antirotation, axial guide arrangements may be resorted to, such as splining, non-circular cross-sectioning and the like.

The fixed outer sleeve 13 is covered at its top by an annular bearing cap of inverted cup-shaped crosssection, which has a threaded connection at 21 onto the top of sleeve 13. Cap 20 is centrally apertured at its top to' receive a tubular bearing bushing 22 of elongated inverted T-shaped section, the bushing 22 presenting a bottom radially and circumferentially continuous flange 23; and a conventional tapered roller bearing 24 is disposed within cap 20, with its inner race resting upon flange 23 and fixedly encircling the tubular axial shank of bushing 22, the outer race of the bearing 24 mating fixedly within the inner axial walls of bearing cap 20. i

The reference numeral 26 designates an internally threaded operator nut of the unit 10, and reference numeral 27 denotes the nuts threadedly mating operating or driving screw. The thus constituted unit 26, 27 is by preference a conventional ball nut sub-assembly by reason of its excellent anti-friction quality; however, an Acme screw and nut type or other type of threading may obviously be employed, depending upon the nature and requirements of the installation. A reduced diameter upper end 28 of screw 27 is provided with a key way 29 for a driving connection to a conventional electric motor M; and for the purpose of the present invention it is contemplated that this motor be equipped with and controlled for its reversal of rotational direction by known current sensitive means, built-in limit switch means or centrifugal reversing switch means, with none of which the present invention is specifically concerned, as indicated in the Summary.

A short transverse take-up pin 31 of Tobin bronze or the like extends through diametrically aligned holes located in shaft extension 29 above the tubular shank of bearing bushing 22, thus coupling these parts for motor-driven rotation, along with the inner race of bearing v 24. A bearing nut 32 is threaded onto the top of the shank of bushing 22, riding downwardly upon an axial thrust needle-type bearing 33 which, in turn, rides in an annular depression on the top of bearing cap 20. An annular bushing 34 is applied about screw shaft extension 28 within nut 32 and above the pin 31.

The operator nut 26 of the unit 10 has an integral, reduced diameter upper extension portion 36, over which an upper annular connector collar or plug 37 of unit 110 is telescoped with a fair clearance, the collar resting upon the larger diameter portion of nut 26, as shown in FIG. 1. As appears in FIG. 2, the reduced extension portion 36 of nut 26 has its annular wall diametrically tapped to receive a pair of opposed set screws '38. These are threaded radially into the nut to terminate short of the latters bore, and they extend radially outwardly with generous clearance into axially aligned holes 39 in the annular upper collar portion 36 of the unit, also radially outwardly into, but not entirely through, corresponding axially opposite holes 40 of a trifle larger in diameter than the set screws 38 for ease in assembly. Yet the screws radially terminate inwardly of the inner diameter of fixed outer guide sleeve 13 to avoid any possibility of rotative running interference.

Annular plug or collar 37 has a threaded connection at 41 (FIG. 1) within the upper end of inner sleeve 14; and it is seen that, with the collar 37 rotated at this connection to bring its radial holes 39 into alignment with the radial holes of inner sleeve 14, the set screws 38, extending as described in radial relation to such holes, serve to interlock collar 37 and inner sleeve 14 for rotation as a unit, under rotation of screw 27 by motor M, to power actuator nut 26 axially in one direction or another; This arrangement constitutes a typical antirotation coupling of the nut through inner sleeve 14 and bottom plug 15 to drive the ram 18 axially.

The lower end of screw 27 is reduced in diameter at 43, where it is surrounded by a metal backing Washer 44 resting atop'the bottom plug 15, and the washer being sustained on that side by a castellated nut 45 threaded upwardly on the screw reduction 43. A cotter pin 46 locks nut 45 in adjusted place. r

The reference numeral 47 generally designates a special retainer of unit 10, which pilots into and, rests downwardly upon washer 44. Retainer 47 is annularly undercut peripherally'at 48 to accommodate an antifriction ring 49 of Teflon, bronze or other appropriate bearing material, upon which retainer 47 may have slight limited rotative slide. Ring 49 thus acts as a pilot to center the screw structure within inner sleeve 14, also to axially back up retainer 47. I

Said retainer is shaped at its top to provide a cylindrical upright wall flange 50, in the cavity of which a resil ient stop cushion 51 of urethane or other equivalent resiliently deformable cushion material, is disposed in snug encircling engagement about the reduced portion 43 of screw 27. There is a slight radial clearance between retainer wall or flange 50 and the cushion pad 51; and an impact-transmitting metal washer 52 rides flush atop the cushion 51, the lower end of the threaded portion of screw 27 being received in a top cavity of washer 52. Retainer 47 is axially piloted exter nally by the anti-friction ring 49 and internally by the washer 44.

Thus, it is seen that, upon rotation of actuator screw 27 the rotatively restrained nut 26, along with correspondingly restrained inner sleeve 14 and ram connector plug 15, will be driven for an axial stroke S of, say,

, 24 inches. Reaching the lower end of this stroke, nut 26 inner sleeve 14, these holes and the nut holes 39 being bottoms downwardly upon impact washer 52, thereby instantaneously compressing the urethane cushion 51; and the latter expands radially, as indicated by arrows and dot-dash line in H0. 1, sufficiently to radially outwardly engage the retainer flange 50.

There is an attendant instantaneous increased frictional torque loading of screw 27 and its drive motor M; automatic means as described-above then come into operation to substantially instantaneously reverse the drive direction of the motor, but without significant shock, noise or undue torque-loading of parts. As this happens, energy has been wound up in cushion 51 which, instantaneously upon motor reversal, reacts to mechanically accelerate an upward cushioned or soft" return of the nut 26 and associated sleeve and upper plug components.

The same substantial effect takes place when nut 26 reaches the upper end of its stroke and halts. A reactive axial thrust effort is instantaneously transmitted to screw 27, cushioned by a compression of pad 51 beneath the screws body. There is a substantially instant torsionally loaded response on the screw shaft 28, causing the current-sensitive switch means, built-in limit switch means or centrifugal switch means (referred to above) to reverse again the direction of rotation of motor M, again without objectionable shock, noise or undue parts-stressing effects. Having thus entered into a reversing mode, the motor's torque receives a cushioned assist at the outset of the reversed and downward stroke.

What is claimed is:

l. A reversing screw actuator unit, comprising threadedly mating screw and nut members motorpowered for reverse driving motions in opposite directions axially of said members, one of which members is rotatable and the other of which is restrained from rotation, an operated load member, and means fixedly connecting said operated member to one of said mated members for an anti-shock motorized reversing drive of said operated member by one of said members in moving axially as the result of said threaded mating of the members, comprising resilient means deformingly engaged by said last-named one of said screw and nut members at the ends of driving motion thereof in both axial directions to terminate said motion, thereby imposing an additional reactive torque load on an axially relatively non-moving one of said screw and nut members, and means responsive to said reactive load to initiate 'a reversal of direction of the motor-powering of said members.

2. A reversing screw actuator unit, comprising threadedly mating screw and nut members motor powered for reverse driving motions in opposite directions axially of said members, one of which members is rotatable and the other of which is restrained from rotation, a reciprocably operated load member, and means fixedly connecting said operated member to one of said mated members for an anti-shock motorized reversing reciprocatory drive of said operated member by one of said members in moving axially as the result of said threaded mating of the members, comprising a resilient cushion pad compressively engaged by said last-named one of said screw and nut members at the ends of driving motion thereof in both axial directions to terminate said motion, thereby imposing an additional reactive torque load on an axially relatively non moving one of said screw and nut members, and means responsive to means is a non-rotating, axially traveling nut member.

6. The actuator unit of claim 2, in which said one of said members compressively engaging said cushion pad is a non-rotating, axially traveling nut member.

7. The actuator unit of claim 4, in which the cushion pad, in being compressively engaged by said nut member, is operatively engaged axially with said screw means to impose an added torsion load on the latter, and thereby additionally load the motor-powering of said screw and nut members.

8. The actuator unit of claim 6, in which the cushion pad, in being compressively engaged by said nut member, is operatively engaged axially with said screw means to impose an added torsion load on the latter, and thereby additionally load the motor-powering of said screw and nut members. I

9. The actuator unit of claim 2, in which said cushion pad is compressed in the direction of the axis of the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.

10. The actuator unit of claim 4, in which said cushion pad is compressed in the direction of the axis of the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.

11. The actuator unit of claim 6, in which said cushion pad is compressed in the direction of the axis of the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.

12. The actuator unit of claim 8, inwhich said cushion pad is compressed in the direction of the axis of the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.

13. The actuator unit of claim 8, in which there is an impact member interposed axially between said cushsaid reactive load to initiate a reversal of direction of is a nut member.

5. The actuator unit of claim l, in which said one of said members deformingly engaging said resilient ion pad and said screw member to operatively engage the compressed pad with the screw member.

14. The actuator unit of claim 12, in which there is an impact member interposed axially between said cushion pad and said screw member to operatively engage the compressed pad with the screw member.

15. The actuator unit of claim 2, in which said reciprocably operated load member has an elongated tubular part fixedly connected thereto, said part enclosing said screw and nut members and being drivingly connected to one of the latter.

16. The actuator unit of claim 6, in which said recip-. rocably operated load member has an elongated tubular part fixedly connected thereto, said part enclosing said non-rotating nut member and being drivingly connected to the latter for axial travel therewith upon rotation of the screw member.

- I i l 

1. A reversing screw actuator unit, comprising threadedly mating screw and nut members motor-powered for reverse driving motions in opposite directions axially of said members, one of which members is rotatable and the other of which is restrained from rotation, an operated load member, and means fixedly connecting said operated member to one of said mated members for an antishock motorized reversing drive of said operated member by one of said members in moving axially as the result of said threaded mating of the members, comprising resilient means deformingly engaged by said last-named one of said screw and nut members at the ends of driving motion thereof in both axial directions to terminate said motion, thereby imposing an additional reactive torque load on an axially relatively non-moving one of said screw and nut members, and means responsive to said reactive load to initiate a reversal of direction of the motor-powering of said members.
 2. A reversing screw actuator unit, comprising threadedly mating screw and nut members motor powered for reverse driving motions in opposite directions axially of said members, one of which members is rotatable and the other of which is restrained from rotation, a reciprocably operated load member, and means fixedly connecting said operated member to one of said mated members for an anti-shock motorized reversing reciprocatory drive of said operated member by one of said members in moving axially as the result of said threaded mating of the members, comprising a resilient cushion pad compressively engaged by said last-named one of said screw and nut members at the ends of driving motion thereof in both axial directions to terminate said motion, thereby imposing an additional reactive torque load on an axially relatively non-moving one of said screw and nut members, and means responsive to said reactive load to initiate a reversal of direction of the motor-powering of said members.
 3. The actuator unit of claim 1, in which said one of said members deformingly engaging said resilient means is a nut member.
 4. The actuator unit of claim 2, in which said one of said members compressively engaging said cushion pad is a nut member.
 5. The actuator unit of claim 1, in which said one of said members deformingly engaging said resilient means is a non-rotating, axially traveling nut member.
 6. The actuator unit of claim 2, in which said one of said members compressively engaging said cushion pad is a non-rotating, axially traveling nut member.
 7. The actuator unit of claim 4, in which the cushion pad, in being compressively engaged by said nut member, is operatively engaged axially with said screw means to impose an added torsion load on the latter, and thereby additionally load the motor-powering of said screw and nut members.
 8. The actuator unit of claim 6, in which the cushion pad, in being compressively engaged by said nut member, is operatively engaged axially with said screw means to impose an added torsion load on the latter, and thereby additionally load the motor-powering of said screw and nut members.
 9. The actuator unit of claim 2, in which said cushion pad is compressed in the direction of the axis oF the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.
 10. The actuator unit of claim 4, in which said cushion pad is compressed in the direction of the axis of the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.
 11. The actuator unit of claim 6, in which said cushion pad is compressed in the direction of the axis of the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.
 12. The actuator unit of claim 8, in which said cushion pad is compressed in the direction of the axis of the screw and nut members, and further comprising means disposed in fixed axial relation to said screw member and rigidly limiting said cushion pad, as thus compressed, to a predetermined degree of radial expansion.
 13. The actuator unit of claim 8, in which there is an impact member interposed axially between said cushion pad and said screw member to operatively engage the compressed pad with the screw member.
 14. The actuator unit of claim 12, in which there is an impact member interposed axially between said cushion pad and said screw member to operatively engage the compressed pad with the screw member.
 15. The actuator unit of claim 2, in which said reciprocably operated load member has an elongated tubular part fixedly connected thereto, said part enclosing said screw and nut members and being drivingly connected to one of the latter.
 16. The actuator unit of claim 6, in which said reciprocably operated load member has an elongated tubular part fixedly connected thereto, said part enclosing said non-rotating nut member and being drivingly connected to the latter for axial travel therewith upon rotation of the screw member. 